Temperature-actuated overhead door

ABSTRACT

A sliding overhead door is normally maintained in its up position by means of at least two helical torsion springs arranged to apply torque to a rotatable shaft which in turn applies a lifting force to cables secured to the door. One of the torsion springs applies torque to the shaft through a heatfusible connection whereby that torque is released upon fusion of the connection as the result of fire, to allow the door to close against the action of the remaining spring.

United States Patent 1 1 3,559,716

[72] Inventor Arthur F. LOUCkS 2,019,084 10/1935 Miller 160/7 R.D. No.2. Mount Pleasant. Pa. 15666 205933 3 1 1 193 w Jr 160/9 [21 I Appl. N43 2,528.869 1 1/1950 DeLaney.... 160/8 122 Filed Aug. 15 1969 2.966.2l212/1960 FimbeLJr... 160/189 451 Patented Fe 2. 19 3,213,924 lO/l965Crosswell [60/191 3,345.775 /1967 Crosby 16/485 Primary ExaminerPeter MCaun [54] TEMPERATURE-ACTUATED OVERHEAD DOOR A1torneyCushman, Darby &Cushman 5 Claims, 2 Drawing Figs. [52] US. Cl 160/9,

160/ ABSTRACT: A sliding overhead door is normally maintained [51 lltl.Cl 1205f 15/20 in its up position by means of at least two helicaltorsion Fleld of Search 160/1 5. 7. springs arranged to apply torque toa rotatable shaft which in 91 191; 16/485; 49/5' 6 turn applies alifting force to cables secured to the door. One of the torsion springsapplies torque to the shaft through a [56] References heat-fusibleconnection whereby that torque is released upon UNITED STATES PATENTSfusion of the connection as the result of fire, to allow the door837,194 1 1/1906 Charroin 49/6 to close against the action of theremaining spring.

ill a 2 24a 4 44 J0 /2z 9 I p 22 Z6 11 46 PL 50 :2 36 as /8 I ll 1 /6' I1: I {1% /4 4;" 1'

' ..---/& M im t 7 1 /5 n l 1 /6 '1 1 k a 1: .1 /8 /7TEMPERATURE-ACTUATED OVERHEAD DOOR DISCLOSURE This invention relates toimprovements in sliding overhead door structures of a type currently inuse in industry and in homes. In particular the invention relates totorsion springsupported overhead doors wherein the improvement residesin an arrangement which automatically operates to close the door inresponse to an increase in temperature caused by a fire in the vicinityof the door.

Conventional overhead door structures of the general type contemplatedby this invention include a vertically slidable door together with aguide frame for the side edges of the door and a door suspension andsupport arrangement. The latter includes a horizontal rotatable driveshaft carrying on each end a threaded drum on which is wound adoor-lifting cable. One end of each cable is secured to its respectivedrum, and the other end is secured to the lower portion of the door, sothat when torque is applied to the drive shaft in the appropriatedirection a lifting force is transmitted by the drums to the cables. Oneor more variable force torsion springs are arranged to apply liftingtorque to the drive shaft, this lifting force being insufficient toraise the door from a closed position yet sufficient to aid materiallyin raising the door and to retain it in the full open position.Generally the torsion spring is mounted being secured to the drive shaftand the other end being fixed in position as by means of a bracketsecured to an adjacent building wall.

The door itself may be rigid or formed in horizontal sections which arehinged together. In the former case the door moves only in a verticalplane, while in the latter case the door will usually be guided firstupwardly and then rearwardly by means of suitable inclined guide tracks.Doors used in homes as garage doors are generally constructed of wood ormetal. Doors used in industrial buildings may be constructed ofmaterials adapted to resist the transmission of heat in the event of afire.

The term torsion spring refers to a helical or spiral spring tensionedby winding about its axis so that the wound spring applies a forcetangential to its axis. When a rotatable shaft is disposed along theaxis, the tangential force becomes a torque tending to rotate the shift.The magnitude of the force varies with the degree of windup.

So far as is known, overhead doors of the above-described type have notbeen adapted to close automatically in the event of a fire, althoughcertain kinds of automatically closing fire doors are known. One type ofsuch fire door in current use is a horizontally sliding door of rathermassive construction mounted on an inclined track and maintained in theopen position by a weight which holds the door at the higher end of thetrack by means of a cable and pulley arrangement. The cable includes aheat-fusible link which will melt in the event of a nearby fire, therebydisconnecting the weight from the door and allowing the latter to rollby gravity along the inclined track to a closed position. Such doors,intended to remain normally open, are usually of relatively great weightand the track is relatively steeply inclined to assure positive movementof the door, with the result that the door will generate considerablemomentum and requires a massive frame to stop it at the lower end of thetrack. The momentum of the door is also hazardous to life and limb.

Another type of automatically closing fire door is disclosed in U.S.Pat. No. 3,345,775. In this arrangement a vertically movable rigid firedoor is supported in an open position by means of a special assembly oftwo constant force coil band springs connected directly at one end tothe door to effect a liftigggction thereon. One of the connectionsincludes a heatfusible link capable of disconnecting its spring from thedoor to permit the latter to close against the action of the otherspring.

The present invention, as previously stated, relates to a different typeof door mechanism, that is a door mechanism inconcentrically about thedrive shaft with one end of the spring eluding at least one main torsionspring which applies torque to a rotatable drive shaft which in turnwinds or unwinds a pair of door-lifting cables. The inventioncontemplates the combination of a main torsion spring or springstogether with a low-torque auxiliary torsion spring which is releasablyconnected to the drive shaft by a suitable fusible link. The combinationof springs provides sufficient counterbalancing force to hold the doorup. but the mainspring or springs do not provide sufficient torque forthis purpose, with the result that the door will close when theauxiliary spring is disconnected from the drive shaft.

The practical significance of the present arrangement is that it can beincorporated simply and economically in existing doors of the torsionspring type, or it can be incorporated during initial construction ofsuch doors at little or no additional cost. The conventional framingand/or suspension arrangement need not be redesigned or modified, itbeing necessary only to employ a mainspring of lesser lifting power. Theauxiliary spring may be incorporated into the suspension arrangementwithout any changes in the latter except partial disassembly in the caseof an existing door structure. In the preferred embodiment the inventiontakes the form of an adapter for an existing door structure, the adapterincluding a bracket to be mounted to a fixed area adjacent the door forfixing one end of the low-torque auxiliary spring and further includingthe auxiliary spring together with means for connecting the other end ofthe latter to the drive shaft and a heatfusible link capable ofreleasing the torque applied by the auxiliary spring to the drive shaft.

It will be understood that a heat-fusible link refers to any devicewhich includes a solid material which has sufficient strength to effecta suitable mechanical connection and which will melt at a relatively lowtemperature to release the connection. Typical materials are variousmetal alloys having a melting point of about F.

The invention will be further understood from the following detaileddescription of a preferred embodiment taken with the drawings in which:

FIG. 1 is a rear elevational view of an overhead door structureembodying the principles of the present invention; and

FIG. 2 is an enlarged perspective view of the auxiliary spring assemblyof FIG. 1.

The door structure of FIG. 1 includes an overhead sectional door 10having its side edges guided by two spaced-apart guide members 12 in theform of inwardly-facing channels which are adapted to receive rollers 14or the like, the latter being carried by the side edges of the door. Thedoor 10 is constructed of horizontal sections 16 or panels hingedtogether in conventional manner to permit the door to flex into aninclined position when it is moved upwardly to its full open position,as determined by the inclined upper portions of the guide members 12.The latter are secured to the wall of the building or to any fixedsupporting structure 15, as by means of brackets 17.

A mechanism for assisting in supporting the weight of the door 10, sothat it can be raised and lowered by the application of relatively smallforce, includes a pair of lifting cables 18 attached at one end to thelower portion of the door 10 as by brackets 20 near the latters sideedges and attached at their other ends to exteriorly threaded drums 22in a manner to be wound thereon. The drums 22 are fixed to the oppositeend portions of a horizontal rotatable drive shaft 24 which is disposedabove the door 10 when it is in a closed position. The ends of the shaft24 project through the drums 22 and are mounted for rotation withinbrackets 26 which are fixed to the supporting structure 15 as by screws28. At least one main torsion spring assembly 30 is associated with thedrive shaft 24 in a manner to apply a torque thereto in a direction towind up the lifting cables 18, thereby applying a lifting force to thedoor 10. In the conventional arrangement the spring assembly 30 appliesmaximum lifting torque when the door is down and completelycounterbalances the door 10 when it is fully open so that it will remainopen until a small positive force in the opposite direction is applied.

All of the above is conventional in overhead door structures of thetorsion spring-type and has been described in order to place the presentinvention in its proper environment. The system illustrated in HS. 1. inorder to be automatically closable in response to a temperature rise.embodies two features which are not present in a conventional system.First. the main torsion spring assembly 30 is modified to the extentthat it will not counterbalance the door when in the fully openposition. Second, there is provided an auxiliary torsion spring assembly32 which applies sufficient torque to the drive shaft 24, through aheat-releasable connection, that both spring assemblies together willmaintain the door open. Accordingly. the main torsion spring assembly 30requires a spring of lesser torque characteristics than the originallydesigned spring. Usually a spring which applies 50 pounds less force issatisfactory. In practice the weaker spring is employed as originalequipment when the invention is applied to a door manufacturingoperation. When an existing door is being modified to incorporate theinvention, the original spring is generally replaced with the weakerspring, although it may sometimes be feasible to adjust the originalspring in a manner to produce less force.

In either event the mainspring assembly 30 may be operatively connectedto the drive shaft 24 in any conventional manner. Usually the assemblyincludes a so-called winding plug 34 which is a sleeve-like elementadapted to be slid over the shaft 24 and secured thereto as by means ofone or more setscrews 36. A helical torsion spring 38 is also slid overthe shaft 24, and one end of the spring is fixed to the plug 34 in atangential position. The opposite end of the spring 38 is held in afixed position, as by means of a suitable bracket 40 which is attachedto a support pad 42 on the adjacent wall or other fixed area. Afterassembly of these parts, with the setscrews 36 being loose, the spring38 is wound up in the appropriate direction by rotating the plug 34relative to the shaft 24, this being accomplished manually by insertinga rod-like tool in any of several radial holes 44 in the plug 34 andusing the tool as a lever to turn the plug 34. When the correct tensionhas been wound into the spring 38, the setscrews 36 in the plug 34 aretightened against the shaft 24 whereupon the spring 34 exerts a torqueon the shaft 24 when the winding tool is removed.

The auxiliary spring assembly 32, as described previously, includes arelatively small torsion spring 46, which is adapted to be includedeither at initial manufacture of the door system or to be addedsubsequently, together with mounting means for attaching the spring 46to the shaft 24 in a heat-releasable manner. As shown, the spring 46 isa spiral or clock-type spring rather than a helical spring, although thelatter type may be employed if desired. The inner end of the spring 46terminates in an inwardly projecting arm 48 which is force fitted into acomplementary slot in the surface of a sleeve 50. The sleeve 50 ismounted on the drive shaft 24 and is fixed thereto as by means of one ormore setscrews 52 which are axially offset from the spring 46. The outerend of the spring 46 is adapted to be held in a fixed position as bymeans of a suitable mounting bracket 54 which in the final door assemblyis secured to the adjacent wall or other fixed area by screws 56 or thelike.

The heat-releasable connection between the auxiliary spring 46 and thedrive shaft 24 may take various forms. As shown, the outer end of thespring 46 is connected to the bracket 54 by means of a heat-fusible link58 one end of which is hooked through a hole in the spring 46 and theother end of which is secured to the bracket 54 by a screw 60.Alternatively the inner end of the spring 46 may be connected to thesleeve 50 by a heat-fusible link, or the sleeve 50 can be keyed orotherwise drivingly connected to the shaft 24 with heat-fusiblematerial.

In the preferred embodiment, the lifting capacity of the auxiliaryspring 46 should not exceed 50 pounds as this is considered a safeindustrial standard that an average person could lift in an emergency orin normal operating conditions. However, the lifting capacity of theauxiliary spring 46 can vary to meet the needs of different doorsystems. The total door weight in the up position is equal to thecombined spring tensions of the mainspring 38 and the auxiliary spring46. lt is seen, as an example, that if the door weight is 500 pounds,and the auxiliary spring 46 has a tension of 50 pounds, the main torsionspring 38 should have a tension of 450 pounds so that the combined forceof the springs is sufficient to counterbalance the door l0 A lnoperation, when the temperature in the area of the door reaches apredetermined value which will melt the fusible link 58, the latter willcome apart or separate, breaking the tension connection of the auxiliaryspring 46 to the mounting bracket 54 and thereby releasing the torqueapplied by the spring 46 to the shaft 24. The force exerted by the maintorsion spring or springs 38 is not sufficient to counterbalance theweight of the door 10, and the door will descend downwardly in the guidemembers 12 into a closed position. However, the door may be liftedmanually with a small amount of effort equal to the force which waspreviously exerted by auxiliary spring 46. It should be noted in thistype of construction, that spring length and tension of the spring willincrease with each foot of door height.

The invention has its greatest utility in an industrial environmentwhere relatively large areas are separated from each other by one ormore overhead doors, the closing of these doors in the event of firebeing highly desirable in order to reduce cross draft. The automaticclosing feature does not introduce any hazard to persons in the area,because the force of the main torsion spring assembly is sufficient toprevent the door 10 from closing so fast as to cause injury. On theother hand as described above, the door 10 can be opened easily,

because the main spring assembly continues to apply all but, say 50pounds of the force necessary to lift the door 10.

As previously stated, the invention may be utilized during initialmanufacture of a door system or utilized subsequently to modify anexisting door, and in either case no costly departure from conventionalconstruction is involved. When an existing door is to be modified it isnecessary only to partially disassemble the door mechanism to the extentof removing the drive shaft 24 so that the sleeve 50 of the auxiliaryspring assembly 32 may be slid over the shaft 24. The latter is thenreinstalled, after substituting a weaker main spring 38, and theauxiliary spring 38 is wound up to the proper tension, using thepreviously-described conventional technique. It is contemplated that theauxiliary spring 46 in the assembly 32 may be prewound, in which eventno winding is required at the time of installation.

I claim:

1. A door structure comprising: a frame having parallel guide members; adoor mounted for sliding movement in said guide members; a rotatableshaft mounted in proximity to said guide members; means associated withsaid rotatable shaft for transmitting torque on the shaft to a liftingforce on said door; a plurality of variable force torsion springs, eachof said variable force torsion springs, each of said variable forcetorsion springs having one end mounted on said rotatable shaft and theother end secured to fixed means, said plurality of variable forcetorsion springs exerting a combination torque sufficient tocounterbalance said door when in the full open position, the torque ofeither spring alone being insufficient to maintain said door open, andone of said variable force torsion springs being an auxiliary springexerting a torque substantially less than said other variable forcetorsion spring; and heat-fusible connecting means between said auxiliaryspring and said shaft for disconnecting the torque produced by saidauxiliary spring at a predetermined temperature whereby said door willclose in response to fusion of said connecting means.

2. A door structure as described in claim 1 wherein said meansassociated with said rotatable shaft comprises a threaded drum fixedlysecured to said rotatable shaft and a cable having one end secured tosaid threaded drum with the other end being secured to said door.

3. A door structure as described in claim 1 wherein said auxiliaryspring is a spiral clock-type spring.

4. A door structure as described in claim 3 wherein said clock-typespring has one end mounted to said rotatable shaft by suitable means andits other end connected to a mounting bracket by a fusible link.

5 A temperature-sensitive adapter for initiating closing movement of anoverhead door of the type having a rotatable drive shaft, meansconnecting the drive shaft to the door in a manner such that rotation ofthe drive shaft is accompanied by upward or downward movement of thedoor, and main torsion spring means associated with the drive shaft toapply torque thereto in a lifting direction opposite to the torqueproduced by the weight of the door, said adapter comprising: anauxiliary torsion spring wound around a spring-supporting sleeve; firstconnecting means between the inner end of said auxiliary spring and saidsleeve; a mounting bracket adapted to be secured to a fixed areaadjacent the drive shaft of the door structure; second connecting meansbetween the outer end of said auxiliary spring and said bracket wherebysaid auxiliary spring when in a wound condition is capable of exertingtorque on said sleeve; third connecting means associated with saidsleeve for connecting said sleeve in concentric relationship to thedrive shaft in a manner such that torque applied to said sleeve istransmitted to the drive shaft; and a heat-fusible member forming a partof one of said connecting means whereby upon fusion of said member thetorque of said auxiliary spring will be released from the drive shaft topermit the door to close.

1. A door structure comprising: a frame having parallel guide members; adoor mounted for sliding movement in said guide members; a rotatableshaft mounted in proximity to said guide members; means associated withsaid rotatable shaft for transmitting torque on the shaft to a liftingforce on said door; a plurality of variable force torsion springs, eachof said variable force torsion springs, each of said variable forcetorsion springs having one end mounted on said rotatable shaft and theother end secured to fixed means, said plurality of variable forcetorsion springs exerting a combination torque sufficient tocounterbalance said door when in the full open position, the torque ofeither spring alone being insufficient to maintain said door open, andone of said variable force torsion springs being an auxiliary springexerting a torque substantially less than said other variable forcetorsion spring; and heatfusible connecting means between said auxiliaryspring and said shaft for disconnecting the torque produced by saidauxiliary spring at a predetermined temperature whereby said door willclose in response to fusion of said connecting means.
 2. A doorstructure as described in claim 1 wherein said means associated withsaid rotatable shaft comprises a threaded drum fixedly secured to saidrotatable shaft and a cable having one end secured to said threaded drumwith the other end being secured to said door.
 3. A door structure asdescribed in claim 1 wherein said auxiliary spring is a spiralclock-type spring.
 4. A door structure as described in claim 3 whereinsaid clock-type spring has one end mounted to said rotatable shaft bysuitable means and its other end connected to a mounting bracket by afusible link.
 5. A temperature-sensitive adapter for initiating closingmovement of an overhead door of the type having a rotatable drive shaft,means connecting the drive shaft to the door in a manner such thatrotation of the drive shaft is accompanied by upward or downwardmovement of the door, and main torsion spring means associated with thedrive shaft to apply torque thereto in a lifting direction opposite tothe torque produced by the weight of the door, said adapter comprising:an auxiliary torsion spring wound around a spring-supporting sleeve;first connecting means between the inner end of said auxiliary springand said sleeve; a mounting bracket adapted to be secured to a fixedarea adjacent the drive shaft of the door structure; second connectingmeans between the outer end of said auxiliary spring and said bracketwhereby said auxiliary spring when in a wound condition is capable ofexerting torque on said sleeve; third connecting means associated withsaid sleeve for connecting said sleeve in concentric relationship to thedrive shaft in a manner such that torque applied to said sleeve istransmitted to the drive shaft; and a heat-fusible member forming a partof one of said connecting means whereby upon fusion of said member thetorque of said auxiliary spring will be released from the drive shaft topermit the door to close.